The present invention relates generally to felt cutting machines adapted to be used by skilled roofers, repairmen, or the like for cutting widths of roofing felt from a roll. More specifically, the present device relates to a portable roll-supporting carriage which houses a plurality of cutting blades for slitting selective widths of roofing felt to be applied to a commercial "built-up" roof surface. The device is suitable for cutting webs of modified bitumen felts, combination base flashing material, mineral surface cap sheet, and similar standard roofing felt rolls of standard American and Metric widths. The invention is believed most appropriately classified in U.S. utility Class 83.
As will be appreciated by those skilled in the art of roofing construction and repair, roofing felts designed for commercial applications are typically made of a modified bitumen fabric and are conventionally employed for "built-up" flat roofs layered with asphalt. The felt fabric is typically stored on large rolls to facilitate transport and use at the roofing site. A single roll of the felt fabric may range from one to one-half meter wide (thirty-nine to fifty-nine inches) and usually contains roughly one hundred yards of felt. The roofing felt is normally covered with a water- and fire-resistant coating, which provides a stiff, smooth surface. However, the quality and texture of the roofing felt varies greatly among different brands and types of felt available on the market.
The skilled roofer will out the roofing felt into strips. The webs of felt are normally overlapped in staggering, brickwork fashion and "mopped" with a hot asphalt mixture. A typical commercial application requires that several plies of felt be laid over the base layer, which is commonly known as the "starter felt". The width of the starter felt webs is typically one-half the width of a roll of felt. Each subsequent ply may range from eight to twenty-four inches wide, depending on the dimensions of the roof surface.
In the past, a variety of devices have been employed to facilitate longitudinal slitting of roofing felt. Typical prior art felt slitters known to me comprise a rectangular stand supported at a distance from the roof surface upon a multiplicity of rigid, elongated legs. A roll-supporting framework transversing the frame may be manually cranked or motor-powered to control the speed and tension of the felt fabric being cut. One or more cutting blades are installed upon a mounting bridge and adapted to penetrate the felt fabric as it is fed through the device. The blades are typically spaced at regular, fixed intervals upon the bridge to provide cuts of standard widths.
Several prior art felt slitters known to me are currently marketed by various roofing supply distributors. For example, a 1984 publication by Reeves Roofing Equipment Company, San Antonio, Tex., discloses cutter devices known as "Reddi Felt Slitters". One Reddi model was hand-powered and the other motor-powered. Either model was available with a thirty-six or sixty-inch roll carrier. Blackwell Burner Co. advertised the same motor-powered product in its 1986 equipment catalog no. RC-22. More recently, a 1987 catalog produced by Roofmaster, Inc. disclosed a similar forty-inch motor-driven felt slitter device, identified by Model No. 24-5000.
The main disadvantage of the prior art devices is their large size and weight. In order to be positioned upon a roof surface, the prior devices must normally be partially dismantled and hoist from the ground by a rope, crane, or the like. The felt rolls must be removed and carried separately to the roof. Moreover, it is often difficult to locate such prior art devices near the work area, since a smooth roofing surface is required to maintain all four legs level during operation. It would thus seem desirable to provide a roofing felt slitter which is compact and lightweight to facilitate easy transport to the roof and from place to place upon the roof surface.
Additionally, the prior art felt slitting devices known to me are biased to grippingly engage the felt roll and to automatically retract after a cut. The particular feature is undesirable, since it will often retract when the worker inadvertently reduces pressure on the fabric and produces an undesired tear. Unnecessary waste of felt fabric results. Moreover, such tension hinders passage of the felt fabric across the blades unnecessarily. A felt slitter device which permits the free flow of fabric from the roll and thus reduces felt waste would be desired.
These prior art felt slitters generally are not adapted to receive oversized rolls of felt fabric or properly adjust for varying widths and textures of felt. Thus it would seem desirable to provide a felt slitter machine which may be readily adjusted to accommodate rolls of varying sizes and textures.
Finally, many of the prior art devices known to me include multiple cutting blades spaced apart at fixed distances. These devices do not permit easy adjustment of the blades to selectively vary the width of the felt web. Hence it is desirable to provide a cutter with adjustably or removably mounted blades which could be selectively moved to produce webs of different widths.
Use of the prior art slitters has also occasioned numerous injuries. The enforcement of stricter safety standards for workers has recently inspired producers of prior art slitters to provide various types of retrofitting safety shields to cover the blades. The prior art shields, however, are typically extremely bulky and inconvenient and tend to make the felt cutter devices even more cumbersome and difficult to transport. If fitted incorrectly, such shields will catch the felt fabric as it feeds through the machine and shred off pieces or completely tear the felt fabric. It is thus desirable to provide integral safety mechanisms which do not interfere with the efficient operation of the cutter.
Certain related cutter devices have been disclosed in the prior art. Prior art patents known to me which may be of some relevance to the present invention include the following: McPhail, U.S. Pat. No. 4,175,460, issued Nov. 27, 1979; U.S. Pat. No. 4,105,791, issued to Price on Apr. 5, 1977; Pickler, U.S. Pat. No. 3,890,868, issued June 24, 1975; and, U.S. Pat. 4,431,141, issued to Schutz on Feb. 14, 1984.